U.S. patent number 5,373,733 [Application Number 07/999,390] was granted by the patent office on 1994-12-20 for exhaust filter backpressure indicator.
This patent grant is currently assigned to Donaldson Company, Inc.. Invention is credited to Ervin P. Fuchs, Edward A. Steinbrueck, Wayne M. Wagner.
United States Patent |
5,373,733 |
Fuchs , et al. |
December 20, 1994 |
Exhaust filter backpressure indicator
Abstract
An exhaust filter backpressure indicator includes a sensor for
measuring the backpressure and the exhaust system. The sensor sends
a signal which is processed for indicating that an exhaust filter
element is filled. The indicator includes a timer so that a signal
corresponding to pressure must be maintained for a predetermined
period of time before the filled element is indicated. The
apparatus may also include high and low frequency discriminators to
process signals within predetermined signal frequency ranges
corresponding to engine operating speeds. Therefore, depending on
the operation of the vehicle, the element will be indicated as
being filled at either high engine speed operation or low engine
speed operation.
Inventors: |
Fuchs; Ervin P. (Farmington,
MN), Steinbrueck; Edward A. (Eden Prairie, MN), Wagner;
Wayne M. (Apple Valley, MN) |
Assignee: |
Donaldson Company, Inc.
(Minneapolis, MN)
|
Family
ID: |
25546275 |
Appl.
No.: |
07/999,390 |
Filed: |
December 31, 1992 |
Current U.S.
Class: |
73/114.76;
73/49.7 |
Current CPC
Class: |
F01N
11/00 (20130101); B01D 46/46 (20130101); F01N
2550/04 (20130101); F02B 3/06 (20130101); Y02T
10/40 (20130101); Y02T 10/47 (20130101) |
Current International
Class: |
B01D
46/46 (20060101); B01D 46/44 (20060101); F01N
11/00 (20060101); F02B 3/00 (20060101); F02B
3/06 (20060101); G01M 015/00 () |
Field of
Search: |
;73/118.1,49.7
;60/277,291,294,311 ;55/DIG.10 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Patent Abstracts of Japan; vol. 011, No. 218 (M-607) 15 Jul. 1987
& JP,A,62 035 009 (Toyota) 16 Feb. 1987..
|
Primary Examiner: Raevis; Robert
Attorney, Agent or Firm: Merchant, Gould, Smith, Edell,
Welter & Schmidt
Claims
What is claimed is:
1. A method of detecting a loaded exhaust filter element in an
engine exhaust system, comprising the steps of:
sampling the backpressure in the exhaust system upstream of the
filter element in two or more ranges;
measuring the engine speed;
processing engine backpressure frequencies corresponding to the
engine speeds so that only frequencies in predetermined ranges are
sampled;
comparing the backpressure reading to a predetermined pressure
level;
selecting timing periods at which the backpressure readings exceed
the predetermined pressure level wherein signal frequencies sampled
in a first range have a first timer interval and wherein
frequencies sampled in a second range having a second timer
interval;
wherein a backpressure reading exceeding the predetermined pressure
level for a selectable predetermined period signals a loaded filter
indicator wherein the first timer interval is different from the
second timer interval.
2. A method according to claim 1, wherein pressures sampled at a
first signal frequency are compared to a first pressure limit and
wherein pressures sampled at a second frequency are compared to a
second pressure limit.
3. A method of detecting a loaded exhaust filter element in an
engine exhaust system, comprising the steps of:
sampling predetermined ranges of the backpressure in the exhaust
system upstream of the filter element;
measuring the engine speed;
comparing the backpressure reading to a selectable predetermined
pressure level for the engine speed;
providing timing periods at which the backpressure readings exceed
the predetermined pressure level, wherein backpressure signal
frequencies sampled in a first range have a first timer interval
and wherein frequencies sampled in a second range have a second
timer interval;
wherein a backpressure reading exceeding the predetermined pressure
level for a selectable predetermined period signals a loaded filter
indicator wherein the first timer interval is different from the
second timer interval.
4. A method according to claim 3, wherein pressures at backpressure
signal frequencies in two or more ranges are sampled.
5. A method according to claim 3, wherein pressures sampled at a
first frequency are compared to a first pressure limit and wherein
pressures sampled at a second frequency are compared to a second
pressure limit.
6. An exhaust filter backpressure indicator for indicating when the
exhaust filter element in an engine exhaust system is filled,
comprising:
sensing means for measuring the backpressure in the exhaust
system;
indicating means for indicating whether the exhaust filter element
is loaded;
first comparator means for comparing the backpressure to a first
predetermined limit;
second comparator means for comparing the backpressure to a second
predetermined limit;
timing means for measuring the period at which the backpressure
exceeds the predetermined limits;
first delaying means for preventing signalling a loaded filter
element reading to the indication means until the backpressure has
exceeded the first predetermined limit for a predetermined first
period; and
second delaying means for preventing signalling a loaded filter
element reading to the indication means until the backpressure has
exceeded the second predetermined limit for a predetermined second
period wherein the predetermined first period is different from the
predetermined second period.
7. An indicator according to claim 6, further comprising first
engine speed discriminating means for discriminating a first
sampling range of engine operating speeds for the first comparator,
and second engine speed discriminating means for discriminating a
second sampling range of engine operating speeds for the second
comparator.
8. An indicator according to claim 6, further comprising signal
frequency filtering means for filtering signals from the sensing
means.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for
indicating whether an exhaust gas filter element is fully
loaded.
2. Description of the Prior Art
Exhaust filter elements are utilized to filter particulates and
soot from exhaust gases and in particular, diesel exhaust, to clean
the exhaust gases before outletting the gases to the atmosphere. If
the filters fill with soot and particulates and are fully loaded,
the engine flow may be decreased substantially, caused by a
build-up of excessive backpressure in the exhaust system which may
cause damage to and/or decrease performance of the engine. In order
to avoid damage to the engine, sensors may be utilized to measure
the backpressure, so that when the pressure exceeds a predetermined
amount, the operator of the equipment is signalled to indicate that
the backpressure is excessive. The filter is then removed and
replaced, or is regenerated so that the backpressure is brought
back within an acceptable range.
The prior methods for determining when a filter element becomes
fully loaded by utilizing a backpressure sensor has several flaws.
For typical operations for diesel forklifts, the engines are
operated at full throttle for short bursts or at idle. Therefore,
when the accelerator is fully depressed, the backpressure rises
substantially from the increased exhaust flow. The high pressure in
the exhaust system may exceed its acceptable pressure limit for a
short period well before the filter is fully loaded with soot and
may indicate replacement or removal of the filter prematurely. In
addition, problems also arise when the sensors are used on a
variety of different pieces of equipment which have different air
flows, backpressure limits and different operating parameters.
Also, differences in the way the equipment is operated, such as
constantly at full throttle or only occasionally at a higher RPM,
may also affect what would be an acceptable performance limit.
It can be seen then, that an exhaust filter backpressure indicator
is needed which does not signal false fully-loaded readings. It can
also be appreciated that an indicator is needed which can be
adapted to and used with a variety of different size engines and
which also adapts to a variety of operating conditions.
SUMMARY OF THE INVENTION
The present invention is directed to an apparatus and method for
indicating that a filter element has become fully loaded utilizing
engine backpressure related to engine operating conditions. An
engine exhaust filter is placed in the exhaust system to filter
soot and particulates from the exhaust prior to outletting to
atmosphere. As the filter becomes loaded with soot, the
backpressure may rise to levels which decrease engine performance
and/or may cause damage to the engine. Therefore, it is desirable
to determine when the filter has become loaded so that it may be
cleaned and/or replaced. The present invention utilizes a sensor
proximate to the filter to measure backpressure. The sensor sends a
signal corresponding to the backpressure which is compared to a set
pressure limit. If the measured backpressure exceeds the set point,
a timer is actuated. If the backpressure remains above the set
pressure limit until the timer has timed through a predetermined
period, a signal is sent indicating that the element has become
loaded with soot and should be removed. In addition, the apparatus
may utilize signal discriminators to test the backpressure only
when the engine is operating within predetermined engine RPM
ranges.
The timer interval and the backpressure set points may be changed
to adapt to different types of equipment and to different operating
conditions for the equipment. The indicator is re-set automatically
upon removal of the filter for cleaning. Therefore, an operator of
the equipment does not need to perform any additional tasks to
reset the apparatus.
In a second embodiment of the invention, high and low engine RPM
set points are used which have corresponding high and low engine
speed timer intervals. In this manner, differences in operating
conditions may be taken into account so that the higher RPM range
is closer to a full throttle operating conditions and the lower RPM
range is closer to an idle or low load throttle operating
condition. Each of these may also have an independently set timer
interval. When the engine is operating at RPM's producing
frequencies within the discriminator range for each of the
associated RPM ranges, the timer is actuated when the backpressure
limit for those frequencies is exceeded. If the timer at either RPM
range is timed out, then an indication of a loaded element is
given.
For the embodiment which utilizes two RPM range discriminators, the
backpressure at two different frequencies is checked so that
different engine operating conditions can be monitored more
closely. The intervals and set points for each of these engine
speed ranges and the engine speed ranges which are sampled may all
be changed independently to adapt to different operating parameters
for different engine systems. In this manner, great flexibility is
obtained with a relatively simple sampling method and
apparatus.
These and various other advantages and features of novelty which
characterize the invention are pointed out with particularity in
the claims annexed hereto and forming a part hereof. However, for a
better understanding of the invention, its advantages, and the
objects obtained by its use, reference should be made to the
drawings which form a further part hereof, and to the accompanying
descriptive matter, in which there is illustrated and described a
preferred embodiment of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings, wherein like reference numerals and letters
indicate corresponding elements throughout the several views:
FIG. 1 shows a diagrammatic view of a first embodiment of an
exhaust filter backpressure indicator according to the principles
of the present invention;
FIG. 2 shows a flow chart of a method of detecting a loaded filter
element for use with the embodiment shown in FIG. 1;
FIG. 3 shows a graph of backpressure corresponding to changing
engine speed in a filter element versus time for an interval after
the element has been loading for a period of time for the
embodiment shown in FIG. 1;
FIG. 4 shows a diagrammatic view of a second embodiment of an
exhaust filter backpressure indicator according to the principles
of the present invention;
FIG. 5 shows a portion of a flow chart of a method for use with the
exhaust filter backpressure indicator shown in FIG. 4;
FIG. 6 shows an additional portion of the flow chart shown in FIG.
5; and,
FIG. 7 shows a graph of backpressure in a filter element versus
time for an interval after the element has been loading for a
period of time, with high and low pressure set points utilized for
the embodiment shown in FIG. 4.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
Referring now to the drawings, and in particular to FIG. 1, there
is shown a diagram of a first embodiment of an exhaust filter
backpressure indicator apparatus, generally designated 10. The
exhaust filter backpressure indicator apparatus 10 is utilized to
indicate that a filter element is fully loaded. The apparatus 10
has a pressure sensor 12 mounted in the exhaust system proximate to
the filter. The indicator apparatus 10 includes an initializer 32,
a system check and error circuit 16, and error indicator 18. The
backpressure indicator apparatus 10 utilizes a signal filter 14 for
filtering pressure signals from the sensor 12 for signal
processing. The indicator apparatus 10 has multiple pressure set
points 20 for different backpressure limits. The limits may be
changed so that the indicator 10 may be adaptable to different size
systems. The set limits 20 are compared to the measured pressure at
a comparator 22. A timer 24 and interval selector 26 are utilized
to measure the period during which the measured pressure exceeds
the chosen pressure set point 20. As explained hereinafter, the
measured pressure must exceed the pressure set point for a minimum
period of time before an indication that the filter is fully
loaded.
Upon timing through the period, a signal is transmitted to the
loaded filter indicator 28. The indicator 28 signals the operator
that the filter element is fully loaded and should be cleaned or
replaced. In the preferred embodiment, a reset switch 30 is
automatically actuated upon removal of the filter to reset the
apparatus 10, so that the operator does not have to perform
additional steps to reset the system.
Referring now to FIG. 2, there is shown a flow diagram of the
testing sequence and sampling steps for the embodiment shown in
FIG. 1. When the system is powered up, it will be reset and the
lights and indicators will be initialized as indicated in block 32
of FIG. 1. The reset will occur if the element has been replaced,
as explained hereinafter. If such a reset is not required, the
initialization sequence checks to determine that the ignition for
the vehicle or equipment is active. If the ignition is not active,
the indicators will not turn on. When the ignition has also been
activated, the indicators turn on to indicate whether all lights
are working. Following the delay, the indicators are turned off. At
that point, the interval selector 26 is loaded with the
predetermined interval. The backpressure set points 20 are
typically set prior to installation, but may be changed thereafter.
The signal which has been filtered at block 14 in FIG. 1 which
corresponds to the measured backpressure is compared to the
pressure set point 20 at comparator 22. If the measured
backpressure is higher than the predetermined limit in the error
detection circuit 16 at start-up, the error detection circuit 16
will signal the indicator 18. The operator will then check that the
element has been properly cleaned and replaced, or check for other
problems with the apparatus.
When the error detection has been completed, the comparator 22 will
measure the backpressure against the set point 20. If the
backpressure is not greater than the predetermined level, the timer
24 is reloaded and the system is reset, and the process begins
again. If the backpressure is greater than the set point, the
interval timer 24 is actuated. If the predetermined interval is
exceeded, then the replace filter indicator 28 is actuated. If the
interval is not exceeded, then the system is reset and the process
begins over again. When the indicator 28 has been actuated
indicating that the filter should be replaced, the filter is
removed and replaced, or cleaned and replaced. Removal or
regeneration of the filter automatically actuates the switch 30 to
reset the system. The process begins over with a cleaned or
regenerated filter or a new replacement filter. In this manner, the
operator does not have to take any additional action to reset the
system as the indicator automatically resets.
As shown in FIG. 3, pressure 38 is plotted against time as the
filter element loads with soot particulate. The time interval
represented in FIG. 3 is after a filter element has been loading
for a period of time. Although the periods of idle and full
throttle are shown having an equal length, it can be appreciated
that operating conditions will vary. It can also be appreciated
that the graph is exaggerated for illustrative purposes. The
pressure peaks 42 represent a full throttle condition while the
troughs 44 indicate the operation of the engine at idle. It can be
appreciated that as the filter element becomes loaded, the idling
pressure 44 rises. In addition, the backpressure at full throttle
42 also increases. Typically, the full throttle pressure 42 rises
at a rate faster than the backpressure at idle 44. A predetermined
backpressure set point 40, however, remains constant over time.
When the measured backpressure 38 exceeds the set point 40, the
timer is activated. When the pressure remains above the set point
40 for a duration greater than a predetermined interval 46, a
signal will be sent to the replace filter indicator shown at 28 in
FIG. 1, indicating that the filter is fully loaded. The replace
filter indicator 28 remains on after the initial timing out of the
timer. It can be appreciated that when the interval 46 is not
exceeded, the timer resets and the filled element indicator is not
actuated.
It can also be appreciated that the length of interval 46 can be
adjusted and the pressure set point 40, shown at 20 in FIG. 1, can
be independently adjusted so that different ranges may be utilized
to indicate a fully loaded filter element. These two parameters can
be adjusted so that different operating conditions may be taken
into account for different types of work being performed by the
equipment.
Referring now to FIG. 4, there is shown a second embodiment of the
backpressure indicator according to the principles of the present
invention, generally designated 110. The second embodiment of the
backpressure indicator 110, includes a sensor 112 and a signal
filter 114. The indicator 110 also includes an error detection
circuit 116 and error indicator 118. Unlike the first embodiment
10, the second embodiment 110 includes a first backpressure trip
set point 120 and a second backpressure trip set point 140. In
addition, the indicator 110 includes a first comparator 122 and a
second comparator 142, as well as a first timer 124 and second
timer 144. The indicator 110 also includes a first timed interval
selector 126 associated with the timer 124 and second timed
interval selector 146 associated with the timer 144. The apparatus
has a replacement indicator 128 and a reset 130. The indicator 130
also has an initializer 132, a low frequency discriminator 134 and
a high frequency discriminator 138 for monitoring in selected
engine operating frequencies.
As shown in FIGS. 5 and 6, the sequence for error detection and
backpressure indication is shown for the second embodiment of the
indicator 110, shown in FIG. 4. The process for the second
embodiment is again started by either resetting the system if the
filter has been regenerated or cleaned, or proceeding to check
whether the equipment has an active ignition. If the system must be
reset, the memory is cleared and the indication lights, which had
indicated a filled element, are turned off. If the ignition is not
active, the system is reset until the ignition is found to be
active. When the ignition has been activated, the indicators are
turned on to let the operator check that all lights are working
properly. When the indicator lights have been on a sufficient time
to check whether they are functioning properly, the indicators are
turned off. The low frequency timer 124 is then loaded with an
interval and the high frequency timer 144 is loaded with another
interval. It can be appreciated that the intervals are separately
set so that different intervals may be used for both the high and
low frequency timers. It can also be appreciated that since the
pressure at higher engine frequency is higher than at lower
frequency, the interval for high frequency will be no greater or
less than the low frequency interval.
When the timers 124 and 144 are loaded, the exhaust backpressure is
measured and a system error is indicated at 118 in FIG. 4 if it is
found to be beyond the predetermined limits at start up. If the
backpressure is not beyond a predetermined limit, then the low
frequency discriminator 134 is checked to see whether it is active.
If the low frequency discriminator 134 is active, meaning the
engine speed and corresponding signal frequency is within the range
of the low frequency discriminator, the backpressure is compared to
the low frequency backpressure set point 120. If the backpressure
does not exceed the low frequency backpressure set point 120, then
the low frequency timer is reset and the entire system is again
reset.
However, if the backpressure is greater than the low frequency
backpressure set point 120, the low frequency timer 124 is
activated. If the duration for which the backpressure exceeds the
backpressure set point is beyond the loaded timed interval, the
replace element indicator 128 is actuated. If the timer 124 does
not time out, the timer is reset and the process starts over.
If the low frequency discriminator 134 is not active, then the high
frequency discriminator 138 is checked to see whether it is active.
If the high frequency discriminator 138 is active, meaning the
engine speed and corresponding signal frequency is within the range
of the high frequency discriminator, then the backpressure is
compared to the high frequency backpressure set point 140. If the
backpressure is below the high frequency pressure set point, then
the high frequency timer 144 is reset, the entire system is reset
and the testing process starts over. However, if the backpressure
is beyond the high frequency backpressure set point 140, then the
high frequency timer 144 is actuated. If the timer 144 times out, a
signal is sent to the replace filter indicator 128 and an
indication that the filter needs replacement is given. If the timer
is not timed out, then the system 110 is again reset and the
process begins again.
The backpressure in the system is shown over time as the filter
element loads with soot in FIG. 7. It can be appreciated that the
pressure 150 has peaks 156 at which the throttle is at a higher
range and troughs 158 at which the throttle is idling. It can be
appreciated that as the equipment is operated, the backpressure
will vary up and down as the accelerator is depressed and lifted.
Although the cycles are shown for illustration as having the same
period in FIG. 7, the period when the engine idles and when it is
at full throttle will vary depending on operating conditions. It
will be noted that the pressure at the idle 158 increases over time
as the filter element becomes loaded. It will also be appreciated
that the full throttle backpressure 156 also increases, but
typically at a faster rate than the idle backpressure.
For the second embodiment, the graph shown in FIG. 7 has a first
set pressure limit 152 from the set point 120 shown in FIG. 4 and a
second pressure limit 154, from the set point 140 of FIG. 4. The
limits 152 and 154 have associated timer intervals 160 and 162,
respectively, which begin timing when the associated limits 152 and
154 are exceeded by the backpressure. Although the limits 152 and
154 are shown exceeded by every cycle in FIG. 7, the limits may not
be initially exceeded for a great number of cycles. It can also be
appreciated that the timed intervals 160 and 162 may not be
exceeded for a great number of cycles. However, for illustrative
purposes, values have been exaggerated and only a short period of
the operation is shown.
The set points 152 and 154 and the intervals 160 and 162 can be
varied independently depending upon the parameters and operating
conditions of the equipment. The low frequency discriminator only
samples when the engine is running at frequencies within a
predetermined RPM range. Therefore, when backpressures exceed the
low pressure set point 152 but the engine is operating at a higher
RPM than that required for the discriminator, the interval timer
will not be actuated. Similarly, the high frequency discriminator
will allow sampling and comparison to the high backpressure set
point 154 only when engine RPM's are within the range associated
with the high frequency discriminator. In this manner, different
warnings may be given when the intervals time out at different
engine frequencies. Since operating conditions and uses of
equipment may vary, it may be advantageous to have two different
system indicators for the different uses of the equipment.
It can be appreciated that although only two sets of
discriminators, timers and comparators are shown, it is possible
that third and fourth sets may be added to sample in various other
ranges. For example, the signal could be passed through a fast
fourier transform to create a number of ranges.
In the present invention, peaks of pressure will not always
indicate a loaded filter element as with prior devices. False
readings are avoided, as only readings which indicate that the
backpressure limit has been exceeded for given engine RPM's for a
predetermined time interval will send a signal that the filter
needs replacement. It can also be appreciated that independently
variable set points and intervals, the present invention is easily
adaptable to various types of equipment having various uses and
operating conditions.
It is to be understood, however, that even though numerous
characteristics and advantages of the present invention have been
set forth in the foregoing description, together with details of
the structure and function of the invention, the disclosure is
illustrative only, and changes may be made in detail, especially in
matters of shape, size and arrangement of parts within the
principles of the invention to the full extent indicated by the
broad general meaning of the terms in which the appended claims are
expressed.
* * * * *